[Kernel] Improve log segment code and error messages

Feature request

Which Delta project/connector is this regarding?

<!-- Please add the component selected below to the beginning of the issue title For example: [Feature Request][Spark] Title of my issue -->

• [ ] Spark
• [ ] Standalone
• [ ] Flink
• [X] Kernel
• [ ] Other (fill in here)

Overview

The code in SnapshotManager::getLogSegmentForVersion can be improved and error messages can be better.

Further details

See tests in SnapshotManagerSuite for error messages that can be improved.